The present invention relates to an electrophotographic recording apparatus, particularly an electrophotographic copying machine, which is equipped with a dry process developing unit and, more particularly, to a system installed in the recording apparatus for supplying to the developing unit a single composition type developer, i.e. colored magnetic toner particles. The present invention also relates to a system for replacing carrier which is contained in a dual composition type developer, i.e. a mixture of magnetic carrier and nonmagnetic toner.
Generally, after a dual composition type developer has been used over a long time in a developing unit of a dry process electrophotographic copier, it loses a sufficient frictional charging property due to fatigue of the carrier and other various causes and comes to require replacement. The replacement has heretofore been accomplished by pulling the developing unit out of a housing of the copier and, then, putting it upside down to remove the used carrier, or by discharging the used carrier by a collecting screw into a container which is placed outside the copier housing, followed by charging a fresh supply of carrier. However, such a prior art procedure of replacement has left various problems unsolved such as scattering of the developer around the copier, inconvenience in respect to disposal of the container, and the need for a special jig for charging a fresh developer, disenabling a user to perform the replacement as desired.
Meanwhile, concerning an electrophotographic copier of the type using a single composition type developer, i.e. magnetic toner, a developer hopper provided with an agitator and a toner bottle are usually placed in the vicinity of a developing unit of the copier so that toner flowing out of the toner bottle may be fed from the developer hopper or toner hopper to the developing unit while being agitated by the agitator. Such a toner supply system is apt to cause the toner to be scattered in and around the copier at each time of supply to smear the copier and the clothes of the user and, in addition, requires an extra space in the toner hopper for the rotation of the agitator, which is detrimental to a small-size design of a copier.
A toner supply system may be provided with a cartridge which has an agitator built thereinside, as disclosed in Japanese Patent Laid-Open Publication No. 56-114969/1981. Although the cartridge with an agitator is effective to reduce the dimensions of a hopper, the agitator-in-cartridge scheme would add to the cost and be unfeasible for a disposal type toner supply system. Further, since toner inside the hopper is directly touched by the bottom of the hopper, it is carried thereby every time the cartridge is replaced with new one, causing contamination of hands and clothes.